Primary intrathoracic thyroid is a rare entity, lacking direct connection to the orthotopic gland. However it is even rarer to identify these tissues in asymptomatic patients. Here, we report a patient of incidental primary intrathoracic thyroid tissue in thyroid scintigraphy. A 58-year-old female patient was referred for the evaluation of her thyroid nodules. At thyroid scintigraphy, other than orthotropic gland, there was a substernal mass in thoracic inlet at the mid-line below thyroid with focal Tc-99m and I-131 uptake, acquired in different sessions. Ultrasound and CT confirmed the mediastinal mass without any connection to the thyroid gland. Fine needle aspiration biopsy confirmed benign follicular thyroid concordant with ectopic thyroid gland in the thoracic inlet. Identifying primary asymptomatic intrathoracic thyroid in thyroid scintigraphy is extremely rare which might be more important in a surgery opted patient.